Indoor pools, water parks and natatoriums can benefit from the efficient dehumidification provided by LDACs.  In preparation for a demonstration that will begin in 2011, AILR studied the potential energy savings for installing an LDAC at the Schaefer Athletic and Recreation Center at the Stevens Institute of Technology (Hoboken, NJ).  The Stevens facility houses a 45’ x 75’ pool.  The continuous evaporation from the pool creates a demand for dehumidification within the building as well as for direct heating of the pool to keep it at 80 F.  Dehumidification and temperature control within the building is now provided by a 11,000 cfm, six-row, chilled water coil (45 F entering chilled water) that at design conditions provides 22.0 tons sensible cooling and 14.5 tons latent cooling.  A water-to-water heat exchanger provides up to 681 MBH heating to the pool.  Condensation on the cooler windows of the building is controlled by heating 3,240 cfm of air to raise the air temperature to 120 F (140 MBH) and delivering this air to a perimeter air curtain that blankets the windows.

The liquid-desiccant air conditioner (LDAC) for the pool at the Schaefer Center will eliminate essentially all of the 140 MBH now used to heat the perimeter air and a significant fraction of the 681 MBH that is used to heat the pool.  At the same time, the LDAC will provide 11 tons of latent cooling to the space, which will directly reduce the load on the chilled water coil that now does both sensible and latent cooling.  The LDAC will be installed so that it deeply dries the 3,240 cfm supplied to the perimeter air curtain.  The supply dewpoint for this air will be approximately 38 F, effectively avoiding condensation on the windows without heating the air.  Pool water will directly cool the LDAC, so the latent load served by the LDAC, which approximately equals the evaporative heat loss from the pool, will be returned to the pool.  The 200 MBH that is needed to regenerate the liquid desiccant will be met by recovering heat from a 75 kW CHP system that will be installed at the site.

The air flow through the LDAC will be controlled so that the heat returned to the pool never exceeds the evaporative cooling load on the pool.  Since the source of the problematic condensation on the building’s windows is the evaporation from the pool it is expected that the modulated LDAC will effectively prevent condensation on the windows while never overheating the pool.

Assuming that the equivalent of 2,000 hours per year of full load perimeter air heating now occurs at Schaeffer, the LDAC will save 280 million Btu for this function.  In addition, assuming that the LDAC operates at an equivalent of 2,500 full-load hours per year, it will save 380 million Btu for pool heating while reducing the load on the building’s chilled water loop by 27,500 ton-hours.